Sanctions would target specific members of Mr Mugabe's government
Russia has said it could veto proposed UN sanctions against Zimbabwe's president and his allies, despite agreeing a G8 statement backing them.
Russia has the power to veto any measures at the UN Security Council, which could take a vote this week.
The US and the UK are pushing for a travel ban and assets freeze on Zimbabwe's President Robert Mugabe and 13 of his allies, and an arms embargo.
Several African leaders have also said they oppose sanctions.
They see a government of national unity as a more realistic solution to Zimbabwe's crisis.
Russian President Dmitriy Medvedev said the world was "dissatisfied" with the recent elections.
But he said no decision had been taken at the G8 about "specific decisions" which the UN should take.
BBC UN Correspondent Laura Trevelyan said Russia had not ruled out using its veto, however it could abstain.
Its UN ambassador Vitaly Churkin said sanctions were not appropriate and could undermine the political process.
DRAFT SANCTIONS LIST
Robert Mugabe, President
Constantine Chiwenga, Defence Forces Commander
Emmerson Mnangagwa, Rural Housing Minister
Gideon Gono, Reserve Bank head
Augustine Chihuri, Police chief
Patrick Chinamasa, Justice Minister
Perence Shiri, Air Force chief
David Parirenyatwa, Health Minister
Didymus Mutasa, Security and Lands Minister
George Charamba, President's spokesman
Paradzi Zimondi, Prison Service head
Happyton Bonyongwe, Central Intelligence Organisation head
Sydney Sekeremayi, Defence Minister
Joseph Made, State Minister for Agricultural Engineering
Source: Draft UN Security Council resolution
China also has the power of veto at the UN Security Council and has recently increased economic co-operation with Zimbabwe.
South Africa's UN ambassador Dumisani Khumalo said the proposed measures "could blow the country apart".
"We do not believe at all that Zimbabwe is a threat to international peace and security."
South Africa is currently on the UN Security Council but does not have the power of veto.
But US ambassador to the UN Zalmay Khalilzad said Mr Mugabe would only respond to "pressure".
France's ambassador to the UN has told the BBC he believes those in favour of the resolution have the nine votes out of 15 needed to pass it.
Zimbabwe Information Minister Sikhanyiso Ndlovu told the state-run Herald newspaper that the G8 statement amounted to "international racism".
Mr Mugabe has long blamed Zimbabwe's economic problems on "Western sanctions" but there is no move to impose trade sanctions or other measures which could hurt ordinary Zimbabweans.
The statement called for financial and other measures against individuals "responsible for violence" in Zimbabwe.
The G8 also called for a special UN Security Council envoy to report on the situation in Zimbabwe and help mediate, casting doubt on their confidence in South Africa's President Thabo Mbeki.
He has been the chief mediator so far but has been criticised for being too soft on Mr Mugabe.
The opposition Movement for Democratic Change (MDC) says more than 100 of its supporters have been killed since it won elections in March, some 5,000 are missing and more than 200,000 have been forced from their homes.
It pulled out of a presidential run-off last month, leaving Mr Mugabe unopposed.
Mr Mbeki and the leaders of Senegal and Tanzania told the G8 leaders that sanctions would not solve Zimbabwe's problems.
Mr Mbeki reportedly said that UN sanctions could lead to civil war.
Senegal's leader, Abdoulaye Wade, told the AFP news agency: "I said that sanctions... wouldn't change the regime."
The G8 leaders said they "do not accept the legitimacy of a government that does not reflect the will of the Zimbabwean people".
"We will take further steps, inter alia introducing financial and other measures against individuals responsible for violence [in Zimbabwe]," the statement adds.
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